GitLab

Add feature flag to control the exposure level of new feature during
development.

Bug: 978197
Change-Id: Ie9651ed8d981d6138409cafa30508d849d7b93b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1900305
Commit-Queue: Wenyu Fu <wenyufu@chromium.org>
Reviewed-by: Theresa  <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713107}